The present technology relates to a viewing angle control element capable of switching a viewing angle of a display between a wide viewing angle and a narrow viewing angle, and a display using the viewing angle control element.
It is desirable that a display has a wide viewing angle as much as possible to provide clear images when viewed from any visual angles. In particular, for a liquid crystal display that has been widespread recently, since the liquid crystal itself has a visual angle dependence, various techniques have been developed for the purpose of widening the viewing angle. However, depending on the use environment, a narrow viewing angle is preferred to allow the user alone to visually recognize the displayed contents. In particular, notebook type personal computers, a personal digital assistant (PDA) or mobile phones often are used at a site such as an interior of a train or plane where there are a large number of unidentified persons. In such a use environment, a narrow viewing angle is preferred since it is not desirable from the viewpoint of security protection and privacy protection that a third person in the vicinity looks into the displayed contents. In short, recently, there is an increasing demand for switching the viewing angle of a display between a wide viewing angle and a narrow viewing angle in accordance with the use condition. This demand is not limited to a liquid crystal display, but can be applied commonly to any arbitrary displays.
A technique proposed for coping with such demand is to provide a device for controlling a phase difference in addition to a display device for displaying an image, and to control a voltage to be applied to the device for phase difference control so as to change the viewing angle property (see for example JP 3322197). The Japanese patent of JP 3322197 illustrates a chiral nematic liquid crystal, a homogeneous liquid crystal, a randomly oriented nematic liquid crystal and the like for the liquid crystal mode used in a liquid crystal display device for phase difference control.
It has been disclosed also a configuration for controlling a viewing angle by providing a viewing angle control liquid crystal panel over a display liquid crystal panel, sandwiching these panels with two polarizing plates, and adjusting voltages applied to the viewing angle control liquid crystal panel (see for example, JP H10-268251 A, JP 2005-316470 A). According to JP H10-268251 A, the liquid crystal mode of the viewing angle control liquid crystal panel employs a twist nematic system. JP 2005-316470 A discloses a configuration having a viewing angle control liquid crystal panel provided between two polarizing plates having parallel transmission axes.
The conventional viewing angle control liquid crystal panels as described above respectively control a viewing angle by using the phase difference of the liquid crystal panels. However, since the phase difference occurring in the liquid crystal panels relies on wavelengths, it is difficult to shield simultaneously all of wavelength regions of R (red), G (green) and B (blue) included in the visible light.
Therefore, with the foregoing in mind, it is a feature of the present technology to provide a display that can shield reliably all of the wavelength regions of visible light when viewed in an oblique direction, and a viewing angle control element used for the display.